Existing dressings for reduced pressure therapy or negative pressure wound therapy (NPWT) often can be overly stiff and the pressure sensitive adhesives used to maintain them during use can be prone to leak formation. Thus, it is relatively easy to form leaks between a sealant film of the dressing and the patient's skin, across the border of these films. The formation of a leak usually results in an alarm condition that must be reset by an attending nurse or caregiver. Attending to the leaks that arise during NPWT can consume appreciable resources and decrease caregiver efficiency. In addition, leaks can result in reduced efficacy of treatment for the patient.
In the treatment of some wounds, especially those covering pressure bearing areas, such as the feet and sacral region, and those near high use regions of the body, such as hands, dressings can be prone to curling up during use. This is often referred to as rucking. Rucking can lead to catching of the dressing on adjacent objects, loss of seal and/or exposure of the wound site to the surroundings. Generally, the highly aggressive adhesives currently used in reduced pressure therapy may be particularly prone to this phenomenon, as exposed adhesives are more likely to catch on adjacent surfaces.
Furthermore, highly aggressive adhesives can be painful to remove, especially around sensitive areas of the body. Less aggressive adhesives, however, typically have not fared well in terms of maintaining adhesion for a wide segment of the patient population during patient activity, and in a range of climates commonly experienced in clinical settings.
As the miniaturization trend for NPWT devices continues, successful miniaturization may depend, in part, on the integrity of the seal around the wound provided by the dressing. In addition, the electrical power requirements needed to maintain a vacuum at a wound site covered by a dressing in the presence of a leak can be dramatically higher than that needed to maintain a vacuum in a low or zero leakage condition.
Further, moist wound healing generally needs a dressing with a relatively moderate moisture vapor transfer rate (MVTR). A typical rate for eliciting a moist wound healing environment is less than 35 g/m2/hr, with risk of maceration occurring for values less than about 8 g/m2/hr. Yet, in the peripheral tissues such as the hands or feet, there is a need for a relatively high MVTR, such as 50-90 g/m2/hr, to minimize moisture storage at the tissue interface, which can lead to unwanted maceration. In addition, it is generally accepted that to maintain a vacuum with minimal effort, a dressing should have an MVTR that is generally as low as possible. Further complicating the situation, patients may perspire at different rates, with such rates fluctuating throughout the day due to changes in the local environment, the patient's degree of activity, clothing, etc. These competing goals for MVTR of a dressing along with the uncertainty of wound exudate liberation and perspiration further complicate the design of a suitable dressing.
Particular to applications in NPWT, the oxygen transfer rate (OTR) of the adhesive film of a dressing may affect the power required to maintain a vacuum on the wound site. Thus a combination of MVTR and OTR may need to be considered to improve the design of a dressing for such applications.
Therefore, there exists a need for a dressing that provides improved wound healing for NPWT, avoids leak formation between the dressing and the patient, avoids edge lifting, rolling or rucking of the dressing during use, avoids causing pain to a patient during a change of the dressing and minimizes the power needed to maintain a vacuum at a wound site to which the dressing is applied.